Powdered thermosetting composition for coatings

ABSTRACT

The present invention relates to powdered thermosetting compositions including a binder which comprises a carboxyl group containing amorphous isophthalic acid containing polyester, a carboxyl group containing semi-crystalline polyester, at least 10 parts by weight, based on the total weight of the binder, of a specific glycidyl group containing acrylic copolymer and a curing agent having functional groups reactive with the polyesters&#39; carboxyl groups. The powdered thermosetting compositions are useful for the preparation of powdered paints and varnishes which give low gloss coatings having an outstanding flow, a remarkable weatherability and excellent mechanical properties.

This application is a national stage entry of PCT/EP01/14888, filed onDec. 17, 2001.

The present invention relates to powdered thermosetting compositionscomprising as binder a co-reactable particulate mixture of a carboxylgroup containing amorphous polyester, a carboxyl group containingsemi-crystalline polyester, a glycidyl group containing acryliccopolymer and a curing agent having functional groups reactive with thepolyesters' carboxyl groups. The invention also relates to the use ofsaid compositions for the preparation of powdered paints and varnisheswhich give matt (low-gloss) coatings providing an outstanding flow, aremarkable weatherability and excellent mechanical properties. Theinvention further relates to the matt coatings obtainable from saidcompositions.

Powdered thermosetting compositions are widely used as paints andvarnishes for coating the most various articles. These powders havenumerous advantages. On the one hand the problems associated withsolvents are completely eliminated and on the other hand the powders arenot wasted, since only the powder in direct contact with the article isretained on the article, any excess powder being, in principle, entirelyrecoverable and reusable. For these and other reasons, powdered coatingcompositions are preferred to coating compositions in the form ofsolutions in e.g. organic solvents.

Powdered coating compositions should give coatings which have a goodadhesion to metal substrates like steel or aluminium, a nice flowwithout defects and orange peel, a good flexibility and weatherabilityas well as a good chemical resistance. Besides, powdered coatingcompositions should exhibit a sufficiently high glass transitiontemperature to avoid reagglomeration during handling, transportation andstorage.

The majority of today's coating compositions provide coatings having ahigh gloss after fusion and curing. The gloss measured at an angle of60° in accordance with ASTM D523 is in fact often equal to or indeedeven greater than 90%.

For example, WO 97/20895 discloses powdered thermosetting compositionsincluding a binder consisting of a mixture of semi-crystalline andamorphous polyesters containing carboxyl groups, and a cross-linkingagent with functional groups capable of reacting with the carboxylgroups of the polyesters. The powdered thermosetting compositions areuseful for preparing powdered varnishes and paints and provide coatingshaving a remarkable weather resistance, high gloss and excellentmechanical properties.

WO 91/14745 discloses a thermosetting powder coating compositioncomprising as binder a co-reactable particulate mixture of a carboxylicacid-functional semi-crystalline polyester component and a curing agenthaving groups reactable with carboxylic acid groups. The compositionmay, if desired, include an amorphous polyester, which is said to affordcoatings with improved weathering performance and improved resistance togloss reduction of the coating during outdoor exposure. So-called“hybrid” powder coating compositions comprise an epoxy resin as aco-reactable curing agent. Polyglycidyl-functional acrylic polymers arementioned among numerous other epoxy resins. The coatings obtained fromthese thermosetting powder compositions exhibit a high gloss.

While powdered compositions which provide high gloss coatings with goodappearance and mechanical properties as well as good weather resistanceare known, there is an increasing demand for powdered paints andvarnishes which provide matt coatings of good quality, for example forcoating certain accessories in the automotive industry, such as wheelrims, bumpers and the like, or for coating metal panels and beams usedin construction.

Thus, various methods for manufacturing powdered paints and varnishesthat provide matt coatings, have been proposed.

According to one of these methods one or more matting agents such asdescribed in U.S. Pat. No. 4,242,253, are introduced into the powderedcomposition, in addition to the binder and conventional pigments.

U.S. Pat. No. 3,842,035 relates to a heat curable powder coatingcomposition which, upon curing, gives a matt finish and which comprisesa mixture of a slow curing and a fast curing thermosetting powdercomposition. The two compositions are extruded separately beforedry-blending.

WO 92/01756 describes powder coating compositions comprised of one ormore semi-crystalline hydroxyl polyesters, one or more amorphouspolyesters and one or more hydroxyl acrylic polymers and a blockedpolyisocyanate cross-linking agent. Coatings of the compositions onshaped metal articles exhibit an ASTM D-523-85-60° gloss value of notgreater than 35.

In EP-A-0 551 064 powdered thermosetting compositions comprising asbinder a mixture of a linear carboxyl group containing polyester and aglycidyl group containing acrylic copolymer are described. The acrylicpolymer must have a number averaged molecular weight (Mn) of 4000 to10000 in order to obtain coatings with useful physical properties. Thecompositions are useful for the preparation of powdered paints andvarnishes which produce matt finishes having a gloss value measured atan angle of 60° in accordance with ASTM D523 equal to or less than 15.

Despite the existing variability of methods for producing matt finishes,experience has shown that these methods are all subject to one or moredisadvantages attributed to problems of processing, as well as tooverall coating performances. Problems are particularly relating toreproducibility and reliability of the gloss value.

There is thus still a need for powdered thermosetting compositions,capable of producing matt (low-gloss) coatings which do not exhibit thedefects and drawbacks of the prior art.

In addition there is a sustained effort to improve flexibility andweatherability of the matt finishes in order to get them appropriate forapplications such as coil coating, for example intended for outdoorconstruction purposes, especially for use in regions having a tropicalclimate.

However, when matt finishes are considered, no method is known today forpreparing thermosetting powdered compositions from a single extrusion,which, upon curing provide criteria such as outstanding flow, remarkableweatherability and excellent flexibility and for which low gloss valuesare perceived in a reproducible and reliable manner.

According to the present invention, it now has been surprisingly foundthat by using as binder a co-reactable particulate mixture of a carboxylgroup containing amorphous isophthalic acid containing polyester, acarboxyl group containing semi-crystalline polyester, at least 10 partsby weight of a specific glycidyl group containing acrylic copolymer anda curing agent having functional groups reactive with the polyesters'carboxyl groups, it is possible to obtain powdered thermosettingcompositions which produce coatings exhibiting the desiredcharacteristics.

Thus, according to the present invention there is provided a powderedthermosetting composition including a binder which comprises

-   (a) a carboxyl group containing amorphous isophthalic acid    containing polyester,-   (b) a carboxyl group containing semi-crystalline polyester,-   (c) at least 10 parts by weight, based on the total weight of the    binder, of a glycidyl group containing acrylic copolymer, said    copolymer comprising at least 10 mole % of a glycidyl group    containing monomer and having a number averaged molecular weight    (Mn) of at least 10000, and-   (d) a curing agent having functional groups reactive with the    polyesters' carboxyl groups.

The present composition is useful for preparing low-gloss coatings, i.e.coatings having a gloss value measured at an angle of 60° in accordancewith ASTM D523 equal to or less than 40, preferably less than 35.

In the sense of the present application the term “isophthalic acidcontaining polyester” refers to a polyester which is composed of atleast 10 mole % of isophthalic acid, preferably at least 50 mole %,based on the total acid constituents of the polyester.

The amorphous polyester and the semi-crystalline polyester independentlymay be linear or branched.

The carboxyl group containing amorphous polyester (a) of the presentcomposition is preferably composed of, referring to the acidconstituents, from 10 to 100 mole % of isophthalic acid, preferably 50to 100 mole % and from 90 to 0 mole % of another diacid, such as analiphatic, cycloaliphatic or aromatic diacid, and, referring to thealcohol constituents, from 70 to 100 mole % of neopentyl glycol and/or2-butyl-2-ethyl-1,3-propanediol and from 30 to 0 mole % of of anotherdiol, such as an aliphatic or cycloaliphatic diol. Branching of theamorphous polyester can be obtained by incorporation of a polyacid orpolyol.

The acid constituent of the amorphous polyester, which is not theisophthalic acid, may preferably be selected from one or more aliphatic,cycloaliphatic or aromatic diacids such as fumaric acid, maleic acid,phthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, 1,12-dodecanedioic acid, etc., or thecorresponding anhydrides.

Incorporation of e.g. up to 15 mole % relative to the isophthalic acid,of polyacids having at least three carboxylic acid groups such astrimellitic acid or pyromellitic acid or their corresponding anhydridesor mixtures thereof, induces branching of the polyester.

The glycol constituent of the amorphous polyester, which is not theneopentyl glycol and/or 2-butyl-2-ethyl-1,3-propanediol, may preferablybe selected from one or more aliphatic or cycloaliphatic glycols, suchas ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol,1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,2-methyl-1,3-propanediol, hydrogenated Bisphenol A, hydroxypivalate ofneopentyl glycol, etc.

Incorporation of e.g. up to 15 mole % relative to the neopentyl glycoland/or 2-butyl-2-ethyl-1,3-propanediol, of trifunctional ortetrafunctional polyols such as trimethylolpropane,di-trimethylolpropane, pentaerythrytol or mixtures therefore,

The carboxyl group containing amorphous polyesters (a) of the presentcomposition preferably have an acid number (AN) from 15 to 100 mg KOH/gand in particular from 30 to 70 mg KOH/g.

The carboxyl group containing amorphous polyesters are advantageouslyfurther characterised by:

-   -   a number averaged molecular weight (Mn) ranging from 1100 to        15000 and preferably from 1600 to 8500, measured by gel        permeation chromatography (GPC);    -   a glass transition temperature (Tg) from 40 to 80° C., measured        by Differential Scanning Calorimetry according to ASTM D3418        with a heating gradient of 20° C. per minute; and    -   an ICI (cone/plate) viscosity accordingly to ASTM D4287-88,        measured at 200° C. ranging from 5 to 15000 mPa.s.

The carboxyl group containing amorphous polyester may fulfill one ormore of the above conditions for its acid number, its number averagedmolecular weight, its glass transition temperature and its ICIviscosity. Preferably, the amorphous polyester, however, fulfills all ofthese requirements.

The carboxyl group containing semi-crystalline polyester (b) of thepresent composition is preferably composed of, referring to the acidconstituents, from 75 to 100 mole % of 1,4-cyclohexanedicarboxylic acid,or terephtalic acid, or mixtures thereof and from 25 to 0 mole % ofanother diacid, such as an aliphatic, cycloaliphatic or aromatic diacidand, referring to the alcohol constituents, from 75 to 100 mole % of analiphatic non-branched diol and from 25 to 0 mole % of another aliphaticor cycloaliphatic diol.

Alternatively, the semi-crystalline polyester may be composed of,referring to the acid constituents, from 75 to 100 mole % of linearnon-branched aliphatic diacid and from 25 to 0 mole % of another diacid,such as an aliphatic, cycloaliphatic or aromatic diacid, and referringto the alcohol constituents, from 75 to 100 mole % of aliphaticnon-branched or a cycloaliphatic diol and from 25 to 0 mole % of ofanother aliphatic diol. Branching of the semi-crystalline polyester canbe obtained by incorporation of a polyacid or a polyol or amono-carboxylic acid having at least two hydroxyl groups or a mixture ofthem.

If the acid constituent of the semi-crystalline polyester of the presentcomposition is for 75 to 100 mole % composed of1,4-cyclohexanedicarboxylic acid, or terephthalic acid, or mixturesthereof, the 25 to 0 mole % of another diacid may be selected fromfumaric acid, maleic acid, phthalic acid, isophthalic acid, terephthalicacid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylicacid, succinic acid, adipic acid, glutaric acid, pimelic acid, subericacid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, etc., or thecorresponding anhydrides.

In this case, the alcohol constituent of the semi-crystalline polyesterof the present composition preferably is for 75 to 100 mole % composedof an aliphatic non-branched diol such as ethylene glycol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol,1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, etc. usedin mixture or alone, and for 25 to 0 mole % of of another aliphatic orcycloaliphatic glycol, such as propylene glycol, neopentyl glycol,2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, hydrogenatedBisphenol A, hydroxypivalate of neopentyl glycol, 1,4-cyclohexanediol,1,4-cyclohexanedimethanol, etc.

Otherwise, if the acid constituent of the semi-crystalline polyester ofthe present composition is for 75 to 100 mole % composed of linearnon-branched aliphatic diacid, these may be selected from succinic acid,adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid,sebacic acid. 1,12-dodecanedioic acid, etc. used in mixture of alone.Preferably the linear non-branched aliphatic diacid contains from 4 to 9carbon atoms. The 25 to 0 mole % of another aliphatic, cycloaliphatic oraromatic diacid may be selected from fumaric acid, maleic acid,terephthalic acid, phthalic acid, isophthalic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, etc., or the corresponding anhydrides.

In this case, the glycol constituent of the semi-crystalline polyesterof the present composition is for 75 to 100 mole % composed ofcycloaliphatic diol such as 1,4-cyclohexanedimethanol,1,4-cyclohexanediol or hydrogenated Bisphenol A, etc. used in mixture oralone, or aliphatic non-branched diol such as of ethylene glycol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol,1,14-tetradecanediol, 1,16-hexadecanediol, etc. used in mixture oralone, and for 25 to 0 mole % of of another aliphatic diol or polyol,such as of propylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol,2-butyl-2-ethyl-1,3-propanediol, hydroxypivalate of neopentyl glycol,1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated BisphenolA, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, etc.

Incorporation of e.g. up to 15 mole percentage based on the total of1.4-cyclohexanedicarboxylic acid, or terephtalic acid, or non-branchedaliphatic diacid, of polyacids having at least three carboxylic acidgroups such as trimellitic acid or pyromellitic acid or theircorresponding anhydrides, or of e.g. up to 15 mole percentage based onthe total of aliphatic non-branched diol or cycloaliphatic diol, oftrifunctional or tetrafunctional polyols such as trimethylolpropane,di-trimethylolpropane, pentaerytritol or mixtures of them, inducesbranching of the semi-crystalline polyesters.

The carboxyl group containing semi-crystalline polyesters of the presentcomposition preferably have an acid number (AN) from 10 to 100 mg KOH/gand in particular from 15 to 80 mg KOH/g.

The carboxyl group containing semi-crystalline polyesters areadvantageously further characterised by:

-   -   a number averaged molecular weight (Mn) ranging from 1100 to        17000 and preferably from 1400 to 11200, measured by gel        permeation chromatography (GPC);    -   a fusion zone from 30 to 150° C., measured by Differential        Scanning Calorimetry (DSC) according to ASTM D3418 with a        heating gradient of 20° C. per minute;    -   a glass transition temperature (Tg) from −50 to +50° C.,        measured by Differential Scanning Calorimetry (DSC) according to        ASTM D3418 with a heating gradient of 20° C. per minute;    -   a degree of crystallinity, measured by Differential Scanning        Calorimetry (DSC) according to ASTM D3415 of at least 5 J/g and        preferably at least 10 J/g; and    -   an ICI (cone/plate) viscosity according to ASTM D4287-88,        measured at 175° C. ranging from 5 to 20000 mPa.s.

The carboxyl group containing semi-crystalline polyester may fulfill oneor more of the above conditions for its acid number, its number averagedmolecular weight, its fusion zone, its glass transition temperature, itsdegree of crystallinity and its ICI viscosity. Preferably, thesemi-crystalline polyester, however, fulfills all of the aboverequirements.

The glycidyl group containing acrylic copolymer (c) of the presentcomposition is preferably composed of 10 to 90 mole % of a glycidylgroup containing monomer and from 90 to 10 mole % of other monomerscopolymerisable with the glycidyl group containing monomer.

The glycidyl group containing monomer used in the acrylic copolymer ofthe present composition may be selected from, for example, glycidylacrylate, glycidyl methacrylate, methyl glycidyl methacrylate, methylglycidyl acrylate, 3,4-epoxycyclohexylinethyl (meth)acrylate and acrylicglycidyl ether. These monomers can be used singly or in combination oftwo or more.

The other monomers of the acrylic copolymer copolymerisable with theglycidyl group containing monomer may be selected from:

-   -   40 to 100 mole percentage of acrylic or methacrylic ester        monomers such as methyl acrylate, ethyl acrylate, n-propyl        acrylate, isopropyl acrylate, n-butyl acrylate, n-decyl        acrylate, methyl methacrylate, ethyl methacrylate, n-propyl        methacrylate, isopropyl methacrylate, n-butyl methacrylate,        isobutyl methacrylate, n-amyl methacrylate, n-hexyl        methacrylate, isoamyl methacrylate, allyl methacrylate,        sec-butyl methacrylate, tert-butyl methacrylate, 2-ethylbutyl        methacrylate, cinnamyl methacrylate, crotyl methacrylate,        cyclohexyl methacrylate, cyclopentyl methacrylate, methallyl        methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate,        2-phenylethyl methacrylate and phenyl methacrylate.    -   0 to 60 mole percentage of other ethylenically unsaturated        copolymerisable monomers such as styrene, alkyl-substituted        styrenes and chloro-substituted styrenes, acrylonitrile, vinyl        chloride, vinylidene fluoride and vinyl acetate.

The glycidyl group containing acrylic copolymers of the presentcomposition preferably have an epoxy equivalent weight of 0.3 to 5.0 andpreferably from 1.0 to 3.0 milliequivalents of epoxy/gram of polymer.

The glycidyl group containing acrylic copolymers may further becharacterised by:

-   -   a number averaged molecular weight (Mn) ranging from 10000 to        25000, preferably 10.100 to 25.000, measured by gel permeation        chromatography (GPC);    -   a glass transition temperature (Tg) from 40 to 85° C., measured        by Differential Scanning Calorimetry (DSC), according to ASTM        D3418 with a heating gradient of 20° C. per minute;    -   an ICI (cone/plate) viscosity determined by the ICI method at        200° C. ranging from 50 to 50000 mPa.s.

The glycidyl group containing acrylic copolymer may fulfill one or moreof the above conditions for its epoxy equivalent weight, its numberaveraged molecular weight, its glass transition temperature and its ICIviscosity. Preferably, the acrylic copolymer, however, fulfills all ofthe above requirements.

The curing agent in accordance to the present invention, havingfunctional groups reactive with the polyesters' carboxyl groups, may beselected from:

-   -   polyepoxy compounds preferably being solid at room temperature        and containing at least two epoxy groups per molecule such as,        for example, triglycidyl isocyanulate like the one marketed        under the name Araldite PT810 (Ciba) or the epoxy resin Araldite        PT910 (Ciba); and    -   β-hydroxyalkylamide group containing compounds which preferably        contain at least one, more preferably two        bis(β-hydroxyalkyl)amide groups, for example, those mentioned in        U.S. Pat. No. 4,727,111, U.S. Pat. No. 4,076,917, EP-A-0 322 834        and EP-A-0 473 380.

The carboxyl group containing amorphous polyester and the carboxyl groupcontaining semi-crystalline polyester of the present composition arepreparable using conventional esterification techniques well known inthe art. The polyesters are prepared according to a procedure consistingof one or more reaction steps.

For the preparation of these polyesters, a conventional reactor equippedwith a stirrer, an inert gas (nitrogen) inlet, a thermocouple, adistillation column connected to a water-cooled condenser, a waterseparator and a vacuum connection tube can be used.

The esterification conditions used to prepare the polyesters areconventional, namely a standard esterification catalyst, such asdibutyltin oxide, dibutyltin dilaurate, n-butyltin trioctoate, sulphuricacid or a sulphonic acid, can be used in an amount from 0.05 to 1.50% byweight of the reactants and optionally, colour-stabilisers, for example,phenolic antioxidants such as Irganox 1010 (Ciba) or phosphonite- andphosphite-type stabilisers such as tributylphosphite, can be added in anamount from 0 to 1% by weight of the reactants.

Polyesterification is generally carried out at a temperature which isgradually increased from 130° C. to about 190 to 250° C., first undernormal pressure, then, when necessary, under reduced pressure at the endof each process step, while maintaining these operating conditions untila polyester is obtained, which has the desired hydroxyl and/or acidnumber. The degree of esterification is followed by determining theamount of water formed in the course of the reaction and the propertiesof the obtained polyester, for example the hydroxyl number, the acidnumber, the molecular weight or the viscosity.

When polyesterification is complete, cross-linking catalysts canoptionally be added to the polyester while it is still in the moltenstate. These catalysts are added in order to accelerate cross-linking ofthe thermosetting powder composition during curing. Examples of suchcatalysts include amines (e.g. 2-phenylimidazoline), phosphines (e.g.triphenylphosphine), ammonium salts (e.g. tetrabutylammonium bromide ortetrapropylammonium chloride), phosphonium salts (e.g.ethyltriphenylphosphonium bromide or tetrapropylphosphonium chloride).These catalysts are preferably used in an amount of 0 to 5% with respectof the weight of the polyester.

The glycidyl group containing acrylic copolymer is preparable byconventional polymerisation techniques, either in mass, in emulsion, orin solution in an organic solvent. The nature of the solvent is verylittle of importance, provided that it is inert and that it readilydissolves the monomers and the synthesised copolymer. Suitable solventsinclude toluene, ethyl acetate, butyl acetate, xylene, etc. The monomersare copolymerised in the presence of a free radical polymerisationinitiator (benzoyl peroxide, dibutyl peroxide, azo-bis-isobutyronitrile,and the like) in an amount representing 0.1 to 4.0% by weight of themonomers.

To achieve a good control of the molecular weight and its distribution,a chain transfer agent, preferably of the mercaptan type, such asn-dodecylmercaptan, t-dodecanethiol, iso-octylmercaptan, or of thecarbon halide type, such as carbon tetrabromide, bromotrichloromethane,etc., is also added in the course of the reaction. The chain transferagent is used in amounts of up to 10% by weight of the monomers used inthe copolymerisation.

A cylindrical, double walled reactor equipped with a stirrer, acondenser, an inert gas (nitrogen, for example), inlet and outlet, andmetering pump feed systems are generally used to prepare the glycidylgroup containing acrylic copolymer.

Polymerisation can be carried out under conventional conditions. Thus,when polymerisation is carried out in solution, for example, an organicsolvent is introduced into the reactor and heated to reflux temperatureunder an inert gas atmosphere (nitrogen, carbon dioxide, and the like)and a homogeneous mixture of the required monomers, free radicalpolymerisation initiator and chain transfer agent, when needed, is thenadded to the solvent gradually over several hours. The reaction mixtureis then maintained at the indicated temperature for some hours, whilestirring. The copolymer obtained is subsequently freed from the solventin vacuo.

Preferably, the binder system of the thermosetting powdered compositionof the present invention comprises based on the total weight of thebinder:

-   -   2 to 88.5, preferably 40 to 80 and more preferably 45 to 75        parts by weight of the carboxyl group containing amorphous        isophthalic acid containing polyester,    -   1 to 85, preferably 5 to 40 and more preferably 10 to 30 parts        by weight of the carboxyl group containing semi-crystalline        polyester,    -   10 to 60, preferably 15 to 40 and more preferably 20 to 35 parts        by weight of the glycidyl group containing acrylic copolymer,        and    -   0.5 to 10.0, preferably 1 to 5 and more preferably 2 to 3 parts        by weight of the curing agent having functional groups reactive        with the polyesters' functional groups.

The binder system of the thermosetting composition of the presentinvention is preferably composed in such a way that for each equivalentof carboxyl group present in the amorphous polyester (a) andsemi-crystalline polyester (b) there is between 0.3 and 2.0 andpreferably between 0.6 and 1.7 equivalents of epoxy groups from theacrylic copolymer (c) and between 0.2 and 1.2 and preferably between 0.4and 1.0 equivalents of reactive functional groups of the curing agent(d).

The thermosetting polyester blend (a & b), when needed, can be obtainedby dry blending the amorphous and the semi-crystalline polyester using amechanical mixing procedure as available for the premixing of the powderpaint constituents.

Alternatively the amorphous and the semi-crystalline polyester can beblended in the melt using a conventional cylindrical double-walledreactor or by extrusion such as with the Betol BTS40.

In addition to the essential components described above, compositionswithin the scope of the present invention can also include one or moreadditive(s) such as catalysts, fillers, flow control agents such asResiflow PV5 (Worlee), Modaflow (Monsanto), Acronal 4F (BASF), etc., anddegassing agents such as benzoin (BASF) etc. To the formulation UV-lightabsorbers such as Tinuvin 900 (Ciba), hindered amine light stabilisersrepresented by Tinuvin 144 (Ciba). Other stabilising agents such asTinuvin 312 and 1130 (Ciba), antioxidants such as Irganox 1010 (Ciba)and stabilisers from the phosphonite or phosphite type can be added.

Both, pigmented systems as well as clear lacquers can be prepared.

A variety of dyes and pigments can be utilised in the composition ofthis invention. Examples of useful pigments and dyes are metallic oxidessuch as titaniumdioxide, ironoxide, zincoxide and the like, metalhydroxides, metal powders, sulphides, sulphates, carbonates, silicatessuch as ammoniumsilicate, carbon black, talc, china clay, barytes, ironblues, lead blues, organic reds, organic maroons and the like.

The components of the composition according to the invention may bemixed by dry blending in a mixer or blender (e.g. drum mixer). Thepremix is then homogenised at temperatures ranging from 70 to 150° C. ina single screw extruder such as the BUSS-Ko-Kneter or a double screwextruder such as the PRISM or APV. The extrudate, when cooled down, isgrounded to a powder with a particle size preferably ranging from 10 to150 μm.

The powdered composition may be deposited on the substrate by use of apowder gun such as an electrostatic CORONA gun or TRIBO gun. On theother hand well known methods of powder deposition such as the fluidisedbed technique can be used. After deposition the powder is heated to atemperature between 160 and 320° C., causing the particles to flow andfuse together to form a smooth, uniform, continuous, uncratered coatingon the substrate surface.

Thus, the present invention further relates to the use of the abovedescribed compositions as powdered varnish or paint or for thepreparation of a powdered varnish or paint. The invention furtherrelates to the powdered varnishes or paints consisting of or comprisingthe present powdered thermosetting composition.

Furthermore, the present invention relates to a method of preparing acoating on a substrate comprising the steps of applying the abovevarnish or paint to the substrate and heating the coated substrate tofuse and cure the powdered varnish or paint to obtain the coating.

Furthermore, the present invention also refers to a coating preparableby the above method and a substrate entirely or partially coated withsuch coating.

The following examples are submitted for a better understanding of theinvention but are not intended to restrict the invention thereto.

If not otherwise stated, all amounts are given in parts by weight.

Besides the abbreviations already defined above, Mw stands forweight-average molecular weight, OHN stands for hydroxyl number and Tmstands for fusion zone.

EXAMPLE 1

Preparation of a Glycidyl Group Containing Acrylic Copolymer

80 parts of n-butyl acetate are brought in a double walled flask of 5 lequipped with a stirrer, a water cooled condenser, an inlet for nitrogenand a thermocouple attached to a thermoregulator.

The flask content is then heated and stirred continuously while nitrogenis purged through the solvent. At a temperature of 125° C. a mixture of0.8 parts of tert-butylperoxybenzoate in 20 parts of n-butyl acetate arefed in the flask during 215 minutes with a peristaltic pump. 5 minutesafter this start another pump is started with the feeding of a mixtureof 22 parts of styrene, 24 parts of glycidyl methacrylate, 40 parts ofbutyl methacrylate and 14 parts of methyl methacrylate, during 180minutes. The synthesis takes 315 minutes.

After evaporation of the n-butyl acetate an acrylic copolymer with thefollowing characteristics is obtained:

ICI200° C. (cone/plate) 16000 mPa · s Mn 15000 Mw 38200

EXAMPLES 2 TO 6

Accordingly the procedure as described in example 1, the acryliccopolymers of example 2 to example 6, having the compositions as intable 1, were prepared.

TABLE 1 example 2* example 3 example 4 example 5 example 6* styrene 2222 25.5 23 27.2 glycidyl methacrylate 24 24 12 24 6 butyl methacrylate40 40 46.3 15 49.5 methyl methacrylate 14 14 16.2 38 17.3 n-butylperoxybenzoate 2.0 0.6 0.8 0.8 0.8 Mn 9300 22600 16600 17000 15500 Mw20400 52400 39800 40500 38600 ICI200° C., mPa · s 4200 30000 24000 4000017000 *Comparative examples Ex 2 and 6 are comparative examples becausethe number averaged molecular weight (Mn) of the copolymer obtained inEx 2 is below 10000 and the glycidyl methacrylate content of thecopolymer of Ex 6 is below 10 mole %.

EXAMPLE 7

Synthesis of an Isophthalic Acid Containing Amorphous Polyester

424.0 parts of neopentyl glycol are placed in a conventional four neckround bottom flask equipped with a stirrer, a distillation columnconnected to a water cooled condenser, an inlet for nitrogen and athermometer attached to a thermoregulator.

The flask contents are heated, while stirring under nitrogen, to atemperature of circa 130° C. at which point 217.7 parts of terephthalicacid and 355.2 parts of isophthalic acid and 2.2 parts ofn-butyltintrioctoate are added. The heating is continued gradually to atemperature of 230° C. Water is distilled from the reactor from 180° C.on. When distillation under atmospheric pressure stops, a vacuum of 50mm Hg is gradually applied. After three hours at 230° C. and 50 mm Hg,the following characteristics are obtained:

AN  4 mg KOH/g OHN 83 mg KOH/g

To the first step prepolymer standing at 200° C., 147.7 parts ofisophthalic acid are added. Thereupon, the mixture is gradually heatedto 230° C. After a 2 hour period at 230° C. and when the reactionmixture is transparent, a vacuum of 50 mm Hg is gradually applied. After3 hours at 230° C. and 50 mm Hg, the following characteristics areobtained:

AN 33 mg KOH/g OHN  3 mg KOH/g ICI200° C. (cone/plate) 3500 mPa · s Tg(DSC, 20°/min) 58° C.

EXAMPLE 8

Synthesis of an Isophthalic Acid Containing Amorphous Polyester

A mixture of 395.9 parts of neopentyl glycol and 15.6 parts oftrimethylolpropane is placed in a conventional four neck round bottomflask as for example 7.

The flask contents are heated, while stirring under nitrogen, to atemperature of circa 130° C. at which point 692.8 parts of isophthalicacid, 36.5 parts of adipic acid and 2.5 parts of n-butyl-tintrioctoateare added. The heating is continued gradually to a temperature of 230°C. Water is distilled from the reactor from 180° C. on. Whendistillation under atmospheric pressure stops, a vacuum of 50 mm Hg isgradually applied. After three hours at 230° C. and 50 mm Hg, thefollowing characteristics are obtained:

AN 48 mg KOH/g OHN  3 mg KOH/g ICI200° C. (cone/plate) 4900 mPa · s Tg(DSC, 20°/min) 59° C.

EXAMPLES 9 TO 10

Accordingly the procedure as described in example 8, the amorphouspolyesters of examples 9 and 10, having the compositions as in table 2,are prepared.

TABLE 2 example 9 example 10 neopentyl glycol 413.6 423.8trimethylolpropane 9.3 isophthalic acid 721.4 720.3 AN, mg KOH/g 32 30OHN, mg KOH/g 3 2 ICI200° C., mPa · s 4500 3000 Tg (DSC 20°/min), ° C.63 57

EXAMPLE 11

Synthesis of a Cycloaliphatic Semi-Crystalline Polyester

A mixture of 532.1 parts of 1,4-cyclohexanedimethanol, 15.9 parts oftrimethylolpropane, 591.3 parts of adipic acid and 2.5 parts ofn-butyltintrioctoate is placed in a reactor as for Example 8. The flaskcontents are heated, while stirring under nitrogen to a temperature ofcirca 140° C., at which point water is distilled from the reactor. Theheating is continued gradually to a temperature of 220° C. Whendistillation under atmospheric pressure stops, 1.0 part oftributylphosphite and 1.0 part of n-butyltintrioctoate are added and avacuum of 50 mm Hg is gradually applied. After 5 hours at 220° C. and 50mm Hg, the following characteristics are obtained:

AN 22 mg KOH/g OHN  3 mg KOH/g ICI200° C. (cone/plate) 6500 mPa · sFusion zone 79-96° C.

EXAMPLES 12 TO 15

Accordingly the procedure as described in example 11, thesemi-crystalline polyesters of examples 12 to 15, having thecompositions as in table 3, are prepared.

TABLE 3 example 12 example 13 example 14 example 151,4-cyclohexanedimethanol 448.1 477.3 1,4-cyclohexanediol 467.31,6-hexanediol 508.2 trimethylolpropane 15.5 15.9 adipic acid 638.5165.3 319.8 628.4 1,12-dodecanoic acid 496.0 319.8 AN, mg KOH/g 21 22 3219 OHN, mg KOH/g 3 2 3 2 ICI, mPa · s 8800 3500 3000 3200 (175° C.)(150° C.) (150° C.) (150° C.) Tm, ° C. 39-47 67-77 70-80 48-55

EXAMPLE 16

The polyesters and acrylic copolymers as illustrated above, are thenformulated to a powder according to one of the formulations A or B asmentioned below.

Formulation A Formulation B White paint formulation Brown paintformulation Binder 74.00 Binder 78.33 Kronos 2310 24.67 Bayferrox 1304.44 (white pigment) (pigment) Resiflow PV5 0.99 Bayferrox 3950 13.80(flow control agent) (pigment) Benzoin 0.34 Carbon Black FW2 1.09(degassing agent) (pigment) Resiflow PV5 0.99 (flow control agent)Benzoin 0.35 (degassing agent)

For the preparation of the powder formulation, the carboxyl groupcontaining isophthalic acid containing amorphous polyester resin and thecarboxyl group containing semi-crystalline polyester resin can be usedas a blend or as separate resins. When used as a blend, blending is doneby mixing the respective resins in the molten state using a conventionalround bottom flask.

The powders are prepared first by dry blending of the differentcomponents and then by homogenisation in the melt using a PRISM 16 mmL/D 15/1 twin screw extruder at an extrusion temperature of 85° C. Thehomogenised mix is then cooled and grinded in an Alpine UPZ100.Subsequently the powder is sieved to obtain a particle size between 10and 110 μm. The powder thus obtained is deposited on chromated (Cr6+)aluminium H5005, DIN 50939 with a thickness of 1 mm, by electrostaticdeposition using the GEMA—Volstatic PCG 1 spray gun. At a film thicknessbetween 50 and 80 μm the panels are transferred to an air-ventilatedoven, where curing proceeds for 15 minutes at a temperature of 200° C.

The paint characteristics for the finished coatings obtained fromformulation A (example 16 to 34) and from formulation B (examples 35 and36) with binder compositions as specified in table 4, are summarized intables 5 and 6.

TABLE 4 1 2 3 4* 5* 6* amorphous polyester 50.75 58.00 51.90 62.65 72.5051.90 semi-crystalline polyester 21.75 14.50 13.00 26.85 — 22.20 acryliccopolymer 25.30 25.30 32.40 7.80 25.30 25.90 curing agent 2.20 2.20 2.702.70 2.20 — *the binders 4, 5 and 6 are comparative

TABLE 5 semi- acrylic amorphous crystalline co- curing formulation Abinder polyster polyster polymers agent gloss DI RI Ex 16 1 Ex 7 Ex 14Ex 1 XL552 5 100 120 Ex 17 1 Ex 7 Ex 11 Ex 1 XL552 3 140 100 Ex 18 2 Ex7 Ex 11 Ex 1 XL552 3 80 60 Ex 19 1 Ex 7 Ex 11 Ex 1 PT810 4 80 80 Ex 20 3Ex 8 Ex 12 Ex 1 XL552 25 100 100 Ex 21 3 Ex 8 Ex 12 Ex 4 XL552 31 100 80Ex 22 2 Ex 9 Ex 12 Ex 1 PT910 26 80 80 Ex 23 2 Ex 9 Ex 12 Ex 3 PT910 2080 60 Ex 24 1 Ex 9 Ex 12 Ex 3 XL552 25 120 100 Ex 25 1 Ex 9 Ex 13 Ex 3XL552 12 120 100 Ex 26 1 Ex 9 Ex 15 Ex 3 XL552 26 100 80 Ex 27 1 Ex 9 Ex13 Ex 5 XL552 25 100 80 Ex 28 1 Ex 9 Ex 13 Ex 5 PT910 27 80 80 Ex 29 1Ex 10 Ex 11 Ex 1 XL552 5 140 100 Ex 30* 1 Ex 10 Ex 11 Comp.Ex 2 XL552 85140 120 Ex 31* 4 Ex 10 Ex 11 Ex 1 XL552 36 120 100 Ex 32* 5 Ex 10 — Ex 1XL552 6 20 0 Ex 33* 6 Ex 10 Ex 11 Ex 1 — 5 0 0 Ex 34* 1 Ex 10 Ex 11Comp. Ex 6 XL552 90 100 100 Ex 35 1 Ex 9 Ex 11 Ex 1 XL552 28 120 100 Ex36 2 Ex 8 Ex 12 Ex 5 XL552 30 100 80 *Examples 30 to 34 are comparativeIn table 5: Column 1: indicates the identification number of theformulation Column 2: indicates the binder composition according totable 4 Column 3: indicates the type of amorphous polyester Column 4:indicates the type of semi-crystalline polyester Column 5: indicates thetype of acrylic copolymer Column 6: indicates the type of the curingagent having functional groups being reactive with the polyesters'carboxyl groups where: PT810 = Araldite 810 (Ciba) =triglycidylisocyanurate PT910 = Araldite 910 (Ciba) =diglycidylterephthalate/ triglycidyltrimellitate mixture (75/25) XL552 =Primid XL552 (EMS) = N,N,N′,N′-tetrakis-(2-hydroxyethyl)-adipamideColumn 7: indicates the 60° gloss, measured according to ASTM D523Column 8: indicates the direct impact strength according to ASTM D2794.The highest impact which does not crack the coating is recorded in kg ·cm Column 9: indicates the reverse impact strength according to ASTMD2794. The highest impact which does not crack the coating is recordedin kg · cm

Except for the formulation of reference example 31, where a wrinkle-typefinish is observed, the coatings obtained from the differentformulations all prove to have a very smooth visual perception, free ofany defects.

The different coatings all have a flexibility of 0T or 1T maximum,according to the ASTM D4145-83 T-bending test, with the exception of theformulations of reference examples 32 and 33 where values higher than3T, indicating a huge lack of flexibility, are perceived upon bending.

As clearly appears from table 5:

-   -   the carboxyl group containing semi-crystalline polyester is        necessary for providing flexibility to the coating (comparative        example 32 versus example 29)    -   decreasing the amount of semi-crystalline polyester reduces        flexibility of the derived coating (example 18 versus example        17, example 23 versus example 24)    -   the type of curing agent has no influence on the gloss and minor        influence on flexibility (examples 17 & 19, 27 & 28)    -   when the curing agent is omitted no influence on gloss, yet a        huge influence on flexibility is perceived (comparative example        33 versus example 29)    -   all glycidyl functionality of the acrylic copolymer, within the        range as specified in the present invention, gives low gloss        coatings without influencing flexibility (examples 20 & 21)

However, when an acrylic copolymer, having a too low glycidylfunctionality (glycidyl group containing monomer content is lower than10 mole percentage) as for the acrylic copolymer of example 6, is used,a high gloss value is observed (comparative example 34) for theresulting coating.

-   -   modifying the acrylic copolymer composition (example 27) or the        acrylic copolymer molecular weight (example 23) within the        specifications of the present invention results in matt flexible        finishes.    -   Only when the number average molecular weight is lower than        10000, as for the acrylic copolymer of example 2, a high gloss        finish is observed (comparative example 30).

As appears from table 5, the powdered compositions according to thepresent invention (examples 16 to 29, 35 and 36) thus prove to satisfy aunique combination of properties. They are particularly useful to obtainlow gloss coatings with an outstanding flexibility and flow.

The thermosetting powdered compositions according to the presentinvention are obtained from a single extrusion and give low glossfinishes in a reproducible and reliable way.

Moreover, the powders according to the present invention prove tosatisfy an excellent outdoor resistance comparable to the currently usednowadays commercial available powders.

In table 6, the relative 60° gloss values, recorded every 400 hours,according to ASTM D523, are reported for the coating obtained fromexamples 35 and 36, submitted to the Q-UV accelerated weathering test.In the same table (comparison) are given the weathering results of acarboxylic acid functionalised amorphous polyester obtained by reacting400,6 parts of neopentyl glycol, 22,3 parts of trimethylolpropane and724,7 parts of isophthalic acid, in the same manner as in example 8.

This polyester has an AN of 32 mg KOH/g and a Tg of 59° C., determinedby DSC with a heating rate of 20° C./min. This polyester is formulatedin a 93/7 ratio with PT810 according to the brown paint formulation asin formulation B. Thus, the comparison formulation did not contain anysemi-crystalline polyester or acrylic copolymer.

In this table only gloss reductions until about 50% of the maximum valueare mentioned. Weathering measurements are conducted in a very severeenvironment, i.e. the Q-UV accelerated weathering tester (Q-Panel Co)according to ASTM G53-88 (standard practice for operating light andwater exposure apparatus—fluorescent UV/condensation type—for exposureof nonmetallic materials).

For the results of table 6, coated panels have been subjected to theintermittent effects of condensation (4 hours at 50° C.) as well as thedamaging effects of sunlight simulated by fluorescent UV-A lamps (340nm, 1=0.77 W/m2/nm) (8 hours at 60° C.).

TABLE 6 UV-A (340 nm, I = 0.77 W/m2/nm) Hours example 36 example 35Comparison 0 100 100 100 400 100 99 100 800 99 100 100 1200 98 97 971600 98 96 97 2000 97 97 97 2400 98 96 96 2800 99 94 95 3200 98 88 923600 95 85 89 4000 90 86 87 4400 87 84 84 4800 84 77 79 5200 78 66 765600 77 61 73 6000 74 52 67 6400 53 43 59 6800 54 54 7200 47 49 7600 40

1. Powdered thermosetting composition including a binder which comprises(a) a carboxyl group containing amorphous isophthalic acid containingpolyester, (b) a carboxyl group containing semi-crystalline polyester,(c) at least 10 parts by weight, based on the total weight of thebinder, of a glycidyl group containing acrylic copolymer, said copolymercomprising at least 10 mole % of a glycidyl group containing monomer andhaving a number averaged molecular weight (Mn) of at least 10000, and(d) a curing agent having functional groups reactive with thepolyesters' carboxyl groups.
 2. Composition according to claim 1,wherein the carboxyl group containing amorphous isophthalic acidcontaining polyester consists of 10-100 mole % isophthalic acid and 0-90mole % of another diacid, based on the total of the acid constituents,and 70-100 mole % neopentyl glycol and/or2-butyl-2-ethyl-1,3-propanediol and 0-30 mole % of another diol, basedon the total of the alcohol constituents.
 3. Composition according toclaim 2, wherein the carboxyl group containing amorphous isophthalicacid containing polyester further contains up to 15 mole % of polyacidsrelative to the isophthalic acid and/or up to 15 mole % of polyols,relative to the neopentylglyol and/or 2-butyl-2-ethyl-1,3-propanediol.4. Composition according to claim 1, wherein the carboxyl groupcontaining amorphous isophthalic acid containing polyester has an acidnumber (AN) from 15-100 mg KOH/g, a number averaged molecular weight(Mn) from 1100 to 15000, a glass transition temperature (Tg) from 40-80°C. and an ICI (cone/plate) viscosity at 200° C. from 5-15000 mPa.s. 5.Composition according to claim 1, wherein the carboxyl group containingsemi-crystalline polyester consists of 75-100 mole % of1,4-cyclohexanedicarboxylic acid, or terephthalic acid, or mixturesthereof, and 0-25 mole % of another diacid, based on the total of theacid constituents, and 75-100 mole % of an aliphatic non-branched dioland 0-25 mole % of another aliphatic or cycloaliphatic diol, based onthe total of the alcohol constituents.
 6. Composition according toclaims 1, wherein the carboxyl group containing semi-crystallinepolyester consists of 75-100 mole % of linear non-branched aliphaticdiacid and 0-25 mole % of another diacid, based on the total of the acidconstituents, and 75-100 mole % of an aliphatic non-branched orcycloaliphatic diol and 0-25 mole % of another aliphatic diol, based onthe total of the alcohol constituents.
 7. Composition according toclaims 5, wherein the carboxyl group containing semi-crystallinepolyester further contains up to 15 mole % of polyacids relative to the1,4-cyclohexanedicarboxylic acid and/or terephthalic acid and/or up to15 mole % of polyols, relative to the 75-100 mole % of aliphaticnon-branched and/or cycloaliphatic diols.
 8. Composition according toclaim 1, wherein the carboxyl group containing semi-crystallinepolyester has an acid number (AN) from 10-100 mg KOH/g, a numberaveraged molecular weight (Mn) from 1100-17000, a fusion zone from30-150° C., a glass transition temperature (Tg) from −50 to 50° C., adegree of crystallinity of at least 5 J/g and an ICI (cone/plate)viscosity at 175° C. from 5-20000 mPa.s.
 9. Composition according toclaim 1, wherein the glycidyl group containing acrylic copolymerconsists of 10-90 mole % of a glycidyl group containing monomer selectedfrom the group consisting of glycidyl acrylate, glycidyl methacrylate,methyl glycidyl acrylate, methyl glycidyl methacrylate,3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethylmethacrylate, acrylic glycidyl ether and mixtures thereof and 10-90 mole% of monomers copolymerisable with the glycidyl group containingmonomers.
 10. Composition according to claim 1, wherein the glycidylgroup containing acrylic copolymer has an epoxy equivalent weight of 0.3to 5.0 milliequivalents of epoxy/gram of polymer, a number averagedmolecular weight (Mn) from 10000-25000, a glass transition temperature(Tg) from 40-85° C. and an ICI (cone/plate) viscosity at 200° C. from50-50000 mPa.s.
 11. Composition according to claim 1, wherein the curingagent is a polyepoxy compound or a β-hydroxyalkylamide group containingcompound.
 12. Composition according to claim 1, wherein the bindercomprises, based on the total weight of the binder, (a) 2 to 88.5 partsby weight of the carboxyl group containing amorphous isophthalic acidcontaining polyester, (b) 1 to 85 parts by weight of the carboxyl groupcontaining semi-crystalline polyester, (c) 10 to 60 parts by weight ofthe glycidyl group containing acrylic copolymer, and (d) 0.5 to 10.0parts by weight of the curing agent having functional groups reactivewith the polyesters' carboxyl groups.
 13. Composition according to claim1, further comprising one or more additive(s) selected from the groupconsisting of catalysts, fillers, flow control agents, degassing agents,UV-light absorbers, light stabilizers, antioxidants and otherstabilizers.
 14. Composition according to claim 1, further comprisingone or more dyes and/or pigments.
 15. Method of preparing a compositionas claimed in claim 1 comprising the steps of blending the components ofthe composition to prepare a premix, homogenising the premix at anelevated temperature and grounding the homogenised product to obtain thepowdered thermosetting composition.
 16. Method according to claim 15,wherein in a first step the amorphous polyester and the semi-crystallinepolyester are dry blended or melt blended.
 17. Powdered varnish or paintconsisting of or comprising a composition as claimed in claim
 1. 18.Method of preparing a coating on a substrate comprising the steps ofapplying a powdered varnish or paint as claimed in claim 17 to thesubstrate and heating the coated substrate to fuse and cure the powderedvarnish or paint to obtain the coating.
 19. Coating, preparable by themethod of claim
 18. 20. Substrate entirely or partially coated with thecoating of claim
 19. 21. The composition according to claim 14 whereinthe dyes and/or pigments are metal oxides, metal hydroxides, metalpowders, sulphides, sulphates, carbonates, silicates, carbon black,talc, china clay, barytes, iron blue, lead blue, organic reds andorganic maroons.
 22. The method according to claim 15 wherein theelevated temperature is 70-150° C.
 23. Composition according to claim 6,wherein the carboxyl group containing semicrystalline polyester furthercontains up to 15 mole % of polyacids relative to the linearnon-branched aliphatic diacid and/or up to 15 mole % of polyols,relative to the 75-100 mole % of aliphatic non-branched and/orcycloaliphatic diols.